Q690高强钢在单调荷载下的延性断裂判据研究  

Ductile Fracture Behaviour of Q690 High Strength Steel Under Monotonic Tensile Actions

作　　者：李梦飞 何浩祥 钟国辉[1,2] Mengfei Li;Ho-Cheng Ho;Kwok-Fai Chung(Chinese National Engineering Research Centre for Steel Construction(Hong Kong Branch),The Hong Kong Polytechnic University,Hong Kong 999077,China;Department of Civil and Environmental Engineering,The Hong Kong Polytechnic University,Hong Kong 999077,China)

机构地区：[1]香港理工大学国家钢结构工程技术研究中心香港分中心,中国香港999077 [2]香港理工大学土木与环境工程学院,中国香港999077

出　　处：《钢结构（中英文）》2024年第5期57-63,共7页Steel Construction（Chinese & English）

摘　　要：Q690高强钢由于其优越的强度和自重比在工程结构中受到越来越多的关注。螺栓连接是钢结构节点组成的重要形式,了解Q690钢的延性断裂行为对于研究Q690构件之间螺栓连接的破坏形式至关重要。为了解决这一问题,使用传统的延性断裂分析方法对Q690钢进行了全面的初步研究,包括校准空穴扩张模型(VGM)和应力修正临界应变(SMCS)模型。对标准拉伸试件和不同缺口半径的圆棒缺口试件进行单调拉伸试验,通过对试验数据的分析得到了Q690钢的真实应力-应变关系和在不同应力三轴度下的工程应力-应变曲线。随后对断口进行电镜扫描试验,区分了试验试件的破坏模式,并对断口表面韧窝形成的凸起和凹陷进行分析,计算出Q690钢的特征长度,用于确定后续有限元模型的网格尺寸。建立有限元模型对试验加载过程进行模拟,使用校准后的本构模型计算出的工程应力-应变曲线与试验结果吻合较好。通过提取不同试件延性断裂发生时断裂起始点的应力应变状态确定了空穴扩张模型(VGM)和应力修正临界应变(SMCS)模型的断裂参数,并用其对试验试件的断裂位移进行预测。结果表明,传统的VGM和SMCS模型不能准确预测Q690试件的断裂,预测误差达到了31%和39%。在此基础上,提出了一种改进的孔洞生长模型,充分考虑了应力三轴度对断裂时临界塑性应变的影响。数值分析表明,改进后的断裂模型对试验试件的断裂位移的预测值与实测值吻合较好,平均误差控制在5%以内。研究强调了了解Q690高强钢延性断裂行为的重要性,并提出了一种改进的延性断裂模型,以提高预测其延性断裂的准确性。The increasing utilization of high-strength Q690 steel in engineering structures is attributed to its superior strength-to-weight ratio.Understanding the ductile tensile fracture behavior of Q690 steel is crucial for investigating bolted connections between Q690 members.To address this,a comprehensive pilot study was conducted using conventional ductile fracture analysis methods,including the Void Growth Model(VGM)and the Stress Modified Critical Strain(SMCS)model.Through monotonic tensile tests on standard and notched coupons of varying radii,the true stress-strain relationship as well as the plastic fracture strains were directly measured for different triaxiality ratios of Q690 steel.Then the fracture surface of tested coupons was observed under SEM,and the failure mode was distinguished.After analyzing the valleys and plateaus formed by the dimples,and the characteristic length of Q690 steel was calculated,which was used as the mesh size of the subsequent numerical model.Advanced finite element models were then used to calibrate and validate the fracture parameters of VGM and SMCS model by examining the stress state at the fracture initiation point and predicting load-extension characteristics and elongations at fracture.The numerical results revealed that both the VGM and SMCS models failed to provide satisfactory predictions for elongations at fracture in the test coupons,and the prediction error of them reached 31%and 39%respectively.As a result,a modified void growth model was proposed,which considered the influence of stress triaxiality on the fracture strain.Notably,the numerical analysis showed a good agreement between predicted and measured values of elongations at fracture in the tested coupons,and the average prediction error was controlled with 5%.This study highlights the importance of understanding the ductile fracture behavior of Q690 steel and introduces a promising new fracture parameter for improved fracture analysis accuracy.

关 键 词：高强度钢材 延性断裂 电镜扫描 断裂预测 

分 类 号：TU511.3[建筑科学—建筑技术科学]